V-type filter frame

ABSTRACT

The present invention relates to a molded plastic rectangular front plate for a V-type filter, said front plate having a front surface and a back surface,
     characterized in that   the back surface of the front plate comprises a support structure protruding in a plane substantially perpendicular to the back surface of the front plate and extending along a major portion of the length of a side of the back surface of the front plate such that the thickness of the front plate in the direction from the front surface to the back surface is increased towards the middle and reduced towards the ends of the front plate side. The present invention further relates to a V-type filter frame and a V-type filter assembly comprising such a front plate.

FIELD OF THE INVENTION

The present invention relates to V-type filter assemblies for removingcontaminants from a gas flow.

BACKGROUND OF THE INVENTION

V-type filter assemblies comprising media packs disposed in a framestructure are known. A V-type filter typically includes two or morepairs of filter media packs arranged in a V-configuration. Each filterpack may be comprised of a pleated particulate or gas filter element. Amedia pack is typically formed from a sheet of filter media, e.g. afiberglass sheet, or a nonwoven polyester sheet or membrane media orcombinations thereof or the like, which is pleated to increase theeffective filtering area of the filter body, and provided with coverplates. To provide mechanical support and/or to combine a plurality ofmedia packs, the media pack is typically arranged in a frame structure.

A prior art filter frame for receiving several media packs is shown inU.S. Pat. No. 6,955,696, which discloses a filter frame comprising twoside plates, which have male connection elements, and two frame beamshaving female connection elements, which are interconnected with themale connection elements of the side plates. Thereby a square frame isformed which supports the media packs. In other words, the media packsrest on the frame beams and on support structures of the side plates.

The filter assemblies are typically mounted in a filter holdingstructure. The filter holding structure may for example comprise afilter housing or filter bank grid, with one or more openings in whichthe filter assemblies are fitted.

In high gas flow applications, e.g. in gas turbine systems, filterassemblies such as that described in U.S. Pat. No. 6,955,696 aresubjected to high external forces which can cause deformation of thefilter assembly, resulting in gas leakage between the parts of thefilter assembly or between the filter assembly and the filter holdingstructure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a filter frame, andparticularly a filter frame front plate, that has improved resistance todeformation of the filter assembly in high gas flow applications.

The object is achieved by a filter frame front plate as will bedescribed in detail herein, and a filter frame comprising such a frontplate.

V-type filter frames can comprise first and second side plates and afront plate which is coupled to the side plates. The V-type filterframes are configured to house one or more pairs of rectangular filterpacks, each pair forming a V shape, such that the mouth of the V shapefaces the front plate. The front plate comprises a rectangular or squareperipherally extending rim and parallel troughs extending betweenopposite ends of the front plate for receiving the front edges of filtermedia packs. The front plate comprises one or more apertures configuredto be aligned with the mouths of the V shape filter pack pairs. The sideplates each comprise a front edge portion, located upstream an airflow,and an opposite rear edge portion, located downstream an airflow, and aninner surface, facing the inner clean side of the filter assembly, andan outer surface, facing the outer soiled side of the filter assembly. Afront edge of each filter pack is sealed against the front plate and twoopposite side edges of each filter pack are sealed to the first andsecond side plates respectively.

In accordance with a first aspect of the present invention there isprovided a molded plastic rectangular front plate for a V-type filter,said front plate having a front surface and a back surface,characterized in that the back surface of the front plate comprises asupport structure protruding in a plane substantially perpendicular tothe back surface of the front plate and extending along a major portionof the length of a side of the back surface of the front plate such thatthe thickness of the front plate in the direction from the front surfaceto the back surface is increased towards the middle and reduced towardsthe ends of the front plate side.

It has been found that by the use of support structures in accordancewith the present invention, the resistance to deformation of the filterassembly in high gas flow applications can be significantly improved.This improvement has been surprisingly found to be even higher inpractice than in theory, which is believed to be due to that theaddition of the support structure causes the centre of gravity of thefront plate to be displaced in a direction from the front surface to theback surface of the front plate as compared to the same front plate sidewithout the support structure. This is believed to induce an internaltension in the molded plastic material during injection molding, whichtension counteracts the stress on the front plate caused by the airpressure load during use.

As an additional advantage, the improvement of the resistance todeformation can be achieved without changing the outer dimensions of thefilter frame and with little or no increase in product weight andmaterials consumption.

In accordance with an embodiment the molded plastic rectangular frontplate is formed in a single piece.

In accordance with an embodiment of the molded plastic rectangular frontplate, the front plate is manufactured by injection molding.

In accordance with an embodiment of the molded plastic rectangular frontplate, a lateral view of the support structure has the shape of acircular segment.

In accordance with an embodiment of the molded plastic rectangular frontplate, the support structure is arranged to protrude into an opening ofthe filter holding structure when mounted to a filter holding structure.

In accordance with an embodiment of the molded plastic rectangular frontplate, the support structure causes the centre of gravity of the frontplate to be displaced in a direction from the front surface to the backsurface of the front plate as compared to the same front plate sidewithout the support structure.

In accordance with an embodiment of the molded plastic rectangular frontplate, the presence of the support structure induces an internal tensionin the molded plastic material, which tension counteracts the stress onthe front plate caused by the air pressure load during use.

In a preferred embodiment, the molded plastic rectangular front platecomprises two support structures, arranged at opposite sides of the backsurface of the front plate.

In accordance with an embodiment of the molded plastic rectangular frontplate, the back surface comprises two support structures protruding in aplane substantially perpendicular to the back surface and extendingsubstantially the length of opposite sides of the back surface of thefront plate such that the thickness of the front plate in the directionfrom the front surface to the back surface is increased towards themiddle and reduced towards the ends of the front plate side.

The support structures are preferably arranged at the same sides of thefront plate to which the side plates coupled. In accordance with anembodiment of front plate, the two support structures are arranged toabut the side plates.

In accordance with an embodiment of the molded plastic rectangular frontplate, the front plate further comprises an abutment surface arranged toabut a filter holding structure when mounted thereto.

In accordance with a second aspect of the present invention there isprovided a V-type filter frame for receiving at least one filter mediapack, said V-type filter frame being arranged to be mounted to a filterholding structure, the V-type filter frame comprising a molded plasticrectangular front plate as described herein with reference to the firstaspect, the front plate having a having front surface and a backsurface, and first and second side plates coupled to the back surface ofthe front plate.

In accordance with an embodiment of the V-type filter frame, the backsurface comprises two support structures protruding in a planesubstantially perpendicular to the back surface and extendingsubstantially the length of opposite sides of the back surface of thefront plate, characterized in that said opposite sides are the samesides of the front plate to which the side plates coupled.

In accordance with an embodiment of the V-type filter frame, the twosupport structures are arranged to abut the side plates.

In accordance with an embodiment of the V-type filter frame, the sideplate has at least one V-shaped plate portion extending between a frontedge portion and an opposite rear edge portion of the side plate, withthe mouth of the V shaped portion facing the front edge portion, said atleast one V-shaped portion being defined by a channel arranged toreceive a side edge of a media pack.

In accordance with an embodiment of the V-type filter frame, the frontplate comprises an abutment surface arranged to abut a filter holdingstructure.

The provision of an abutment surface on the front plate ensures optimalsealing properties between the filter holding structure and the filterframe.

In accordance with an embodiment of the V-type filter frame, a sealingmember is provided at the abutment surface of the front plate.

In accordance with an embodiment of the V-type filter frame, the sealingmember comprises a compressible sealing strip.

In accordance with an embodiment of the V-type filter frame, the frontplate is coupled to the side plates by means of a snap-lock element. Amechanical locking element such as a snap-lock will allow a personworking with the mounting of the filter assembly to handle the frameassembly even before an adhesive has been supplied thereto.

In accordance with an embodiment of the V-type filter frame, a rearplate is engaged with rear edge portions of the first and second sideplates by means of a snap lock element. Similar to the use of snap-lockelement between the front plate and side plates, this makes thestructure easier to handle during assembly.

In accordance with third aspect of the present invention, a V-typefilter assembly comprising a filter frame as described herein and atleast one filter media pack arranged in the filter frame is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference tothe appended drawings in which:

FIG. 1 is a schematic view of a filter assembly comprising a moldedplastic rectangular front plate according to the invention;

FIG. 2 is a schematic exploded view of an embodiment of a filter framecomprising a molded plastic rectangular front plate according to theinvention;

FIG. 3 is a schematic view of a molded plastic rectangular front plateaccording to the invention;

FIGS. 4a and 4b are schematic side views of embodiments of a moldedplastic rectangular front plate according to the invention;

FIGS. 5a and 5b are cross-sectional views of filter frame parts of thefilter frame.

It is to be noted that the appended drawings illustrate only exemplaryembodiments of the invention, and are therefore not to be consideredlimiting of its scope. Other, equally effective embodiments may also beencompassed by the invention as claimed. It is contemplated thatfeatures of one embodiment may also be incorporated in other embodimentswithout further recitation.

DESCRIPTION OF PREFERRED EMBODIMENTS

According to an embodiment of the V-type filter assembly 100, shown inFIG. 1, it comprises an embodiment of the filter frame 102, and several,in this embodiment six, media packs 104 carried by the filter frame 102.Although the invention will be described with reference to a 3Vembodiment, it is understood that the invention is equally applicable to1V, 2V, 4V or more V configurations, i.e. filter assemblies comprising2, 4, 8, or more filter media packs. The media packs 104 can be of anysuitable kind, but typically each media pack 104 comprises a sheet offilter media, which has been pleated to an accordion shape in order toincrease the effective filtering area of the filter body. Although thefilter is shown having pleated filter media packs, it is contemplatedthat the filter media packs may be comprised of carbon beds or other gasphase filter medium. The filter media pack 104 may be suitable for atleast one of liquid phase, gas phase, particulate or molecularfiltration. In one embodiment, the filter media pack 104 may be amolecular filtration media, such as bed of carbon or other gas phaseabsorber.

The filter frame 102 comprises a front plate 110, two side plates 112 a,112 b and a rear plate 114, embodied by three separate plate elements116. V-type filters are provided in a wide variety of sizes. A commontype has a substantially square front plate of about 600×600 mm. Theheight of the front plate may vary, but is often 20 mm or 25 mm.

The air flow direction through the filter is indicated by arrow 106. Thedirection of the arrow 106 is orientated as V-type filters are typicallyutilized, but it is contemplated that flow direction through the filtermay also be in the reverse direction.

FIG. 2 depicts an exploded view of the filter frame without the filtermedia packs. The front plate 110 is rectangular and comprises aperipherally extending rim 118, and parallel troughs 120 a, 120 bextending between opposite rim sides 122 a, 122 b of the front plate110. The front plate 110 is formed in a single piece, having a firstcoupling portion 124 a comprising a first groove 126 a at rim side 122a, configured to receive the front edge portion 128 a of the first sideplate, and a second coupling portion 124 b (not shown in FIG. 1)comprising a second groove 126 b at rim side 122 b, configured toreceive the front edge portion 128 b of the second side plate. Eachgroove 126 extends along a respective portion of the rim 118 at aninside thereof, and adjacent thereto. The side plates 112 a, 112 b arearranged at the opposite rim sides 122 a, 122 b of the front plate 110.The side plates include an exterior side and an interior side. Referringnow to FIG. 1, the interior side of each side plate faces the filterelements. Each side plate 112 has a front edge portion 128, adapted tobe received in the groove 126. Each side plate 112 extends perpendicularto the front plate 110, and rearwards therefrom. The media packs 104 areplate shaped and extend obliquely substantially in the direction of theair flow from the front plate 110, although they extend close toperpendicular to the front plate 110. The media packs 104 are arrangedside by side, leaning alternately to one side and to the other side,thereby forming a zigzag structure. More particularly, they are arrangedin pairs, each pair forming a V shape, such that the mouth of the Vshape faces the front plate 110. A front edge of each media pack 104 isreceived in one of the troughs 120, and apertures 130 between thetroughs 120 are aligned with the mouths of the V shapes. Each side plate112 has three V-shaped portions 134 extending between the front edgeportion 128 and an opposite rear edge portion 136 of the side plate 112,with the mouth of each V-shaped portion 134 facing the front edgeportion 128. The V-shaped portions 134 are joined along a minor fractionof their length, extending from the mouth towards the other end, whilethere are gaps between them along a major part of their length.Reinforcing elements 154 may be provided extending between two adjacentV-shaped portions to further increase the structural rigidity of theside plate 112. These reinforcing elements 154 can also serve as handleswhen handling the side plates 112 or (semi-) assembled filter frameassemblies 100. Each V-shaped portion 134 is defined by a channel,having side walls 138. Each V-shaped channel has is adapted to receiveside edge portions, of two media packs 104. Of course, it is alsopossible within the scope of the appended claims for the side plates 112to have additional or less than three V-shaped portions, such as one,two, four or more. Also, the side plates 112 may not have V-shapedportions at all but may for example be provided in the form of coveringhaving a rectangular or trapezoidal shape or similar without openingsbetween adjacent pairs of media packs. Each plate element 116 of therear plate 114 covers rear edge portions of two media packs 104 forminga V-shape. The plate elements 116 each extend between, and are attachedto, a respective fraction of the rear edge portion 136 of each sideplate 112. Consequently, the front plate 110, the side plates 112, andthe rear plate 114 support each other to form a strong filter frame 102,which carries the media packs 104.

The front plate 110 consists of a single molded plastic element having afront surface 110 a and a back surface 110 b. The front plate 110 isrectangular and comprises a peripherally extending rim 118, and paralleltroughs 120 extending between opposite rim sides 112 a, 122 b of thefront plate 110. The rim 118 typically has a substantially rectangularcross section and may be formed of solid plastic, but is typicallyformed at least partially hollow to reduce weight and materialconsumption. The troughs 120 comprise an open channel structure definedby a bottom wall and two opposing longitudinal side walls. The ends ofthe open channel structure are defined by the opposite rim sides 112 a,122 b of the front plate and grooves 126 such that the inner volume ofthe troughs communicates with the grooves 126. The front plate comprisestwo side troughs 120 a arranged adjacent and parallel to opposite rimsides 132 a, 132 b. The side troughs 120 a are configured to receive thefront edge portion of the first and last filter media pack respectively.In a 1V configuration these may be the only troughs. In a 2V, 3V, ormore V, configuration the front plate comprises additional intermediatetrough(s) 120 b arranged between the side troughs 120 a. Theintermediate troughs 120 b are each configured to receive the adjacentfront edge portions two adjacent filter media packs 104. Thus, a 2Vconfiguration will have one intermediate trough, a 3V configuration willhave two intermediate troughs, etc.

The front plate 110 comprises several different integral functionalportions. The functional portions include coupling portions 124 a, 124 bfor connecting the front plate 110 to the side plates 112 a, 112 b,troughs 120 for receiving the front edges of the filter media packs 104,and an abutment surface 140 for mounting and sealing the front plateagainst a holding structure, such as a filter housing or filter bankgrid (not shown). The abutment surface 140 typically has a sealingmember 142, here in the form of a sealing strip made from polyurethaneor similar. As will be described below, the filter frame assembly is tobe fastened by means of clamps or similar, which firmly press the filterframe assembly against a filter holding structure, such as a filterhousing or filter bank grid (not shown). When this is done the sealingmember 142 will be compressed.

The front plate 110 further has two support structures 150 a, 150 b(referred to commonly as 150) for improving the resistance todeformation of the front plate. Each support structure 150 consists of aplate-like element protruding in a plane substantially perpendicular tothe back surface 110 b of the front plate 110 and extendingsubstantially the length of a peripheral side of the back surface of thefront plate such that the thickness of the front plate in the directionfrom the front surface 110 a to the back surface 110 b is increasedtowards the middle and reduced towards the ends of the front plate side.In a lateral view as shown in FIG. 3 and FIG. 4, the support structure150 may have the shape of a circular segment. The support structures 150a, 150 b are arranged directly adjacent the grooves 126 a, 126 bconfigured to receive the front edge portions of the side plates.

In one embodiment, the support structures 150 extend over about 95% ofthe length of the side 122 of the back surface 110 b of the front plate.In another embodiment, the support structures extend over about 80% ofthe length of the side 122 of the back surface of the front plate. Thesupport structures have a thickness in the range of 1 mm to 3 mm and amaximum height of the support structure, i.e. the height of the supportstructure where the perpendicular protrusion is highest, in the range of20 mm to 40 mm.

The front plate 110 is manufactured by injection molding of a suitablethermoplastic, e.g. acrylonitrile butadiene styrene (ABS) copolymer. Theaddition of the support structures 150 a, 150 b to the back surface 110b of the front plate causes the centre of gravity of the front plate tobe displaced in a direction from the front surface to the back surfaceof as compared to an identical front plate side but without the supportstructure. This induces an internal tension in the molded plasticmaterial during injection molding, which tension counteracts the stresson the front plate caused by the air pressure load during use.

In accordance with an embodiment of the molded plastic rectangular frontplate 110, the centre of gravity of the front plate is displaced adistance corresponding to at least 10%, such as at least 15%, such as atleast 20%, of the height of the front plate without the supportstructure. In a front plate having a height, without the supportstructure, of 20 mm, this would correspond to a displacement of centreof gravity of the front plate by at least 2 mm, such as at least 3 mm,such as at least 4 mm. In a front plate having a height, without thesupport structure, of 25 mm, this would correspond to a displacement ofcentre of gravity of the front plate by at least 2.5 mm, such as atleast 3.75 mm, such as at least 5 mm.

The support structure extends along a major portion of the length of aperipheral side of the back surface of the front plate. By “a majorportion of the length” is meant at least 50% of the length of a side ofthe back surface of the front plate. In accordance with an embodiment,the support structure extends along at least 50%, such as at least 60%,such as at least 70%, such as at least 80%, such as at least 90%, of thelength of a side of the back surface of the front plate.

In accordance with an embodiment of the molded plastic rectangular frontplate, the thickness of the support structure is in the range of 1 mm to5 mm, such as in the range of 1 mm to 4 mm, such as in the range of 1 mmto 3 mm.

In accordance with an embodiment of the molded plastic rectangular frontplate, the maximum height of the support structure, i.e. the height ofthe support structure where the perpendicular protrusion is highest, isin the range of 10 mm to 50 mm, such as in the range of 10 mm to 40 mm,such as in the range of 10 mm to 30 mm.

In accordance with an embodiment of the molded plastic rectangular frontplate, the maximum height of the support structure, i.e. the height ofthe support structure where the perpendicular protrusion is highest,amounts to in the range of 10 to 80%, such as in the range of 20 to 70%,such as in the range of 30 to 60%, of the thickness of the front platein the direction from the front surface to the back surface.

FIGS. 4a and 4b show two different embodiments of the front plate 110.

FIG. 4a shows a front plate having a height, without the supportstructure, of 20 mm. Centre of gravity without the support structure is10 mm from the front surface. Centre of gravity with the supportstructure is 15.71 mm from the front surface. In this embodiment, thesupport structure extends along about 90% of the length of a side of theback surface of the front plate.

FIG. 4b shows a front plate having a height, without the supportstructure, of 25 mm. Centre of gravity without the support structure is12.5 mm from the front surface. Centre of gravity with the supportstructure is 16.46 mm from the front surface. In this embodiment, thesupport structure extends along about 80% of the length of a side of theback surface of the front plate.

In the V-type filter frame, the inner volume of the troughs 120 mayoptionally communicate with the grooves 126. This allows for a fluidadded to the troughs 120 to flow, by force of gravity or capillary forceinto the grooves 126. As shown in FIGS. 5a and 5b , the troughs 120 arefluidly connected with the grooves 126 by channels 160 starting at thebottom 162 of the troughs 120, where the side plates 112 are connectedto the front plate 110. In an embodiment, the bottom portion of thetroughs of the front plate is sloped downward towards the couplingportions of the front plate so as to direct fluid in the trough towardsthe fluid connections. This ensures that fluid added to the troughs 120is brought into contact with the channels 160. The troughs may also beprovided with glue guides, e.g. in the form of protrusions at the bottomportion of the troughs creating a distance between the filter media packedge and the trough bottom, to allow adhesive to spread more efficientlyin the trough.

The depth of the groove 126 is slightly larger than the length of thefront edge portion 128 of the side plate to be inserted. Accordinglywhen the side plate 112 is coupled to the front plate 110, a void 164 isformed in the groove 126 between the front plate and the front edgeportion of the side plate.

According to an embodiment, the channel 160 is such that a fluiddeposited in the trough 120 can pass through said channel and into avoid 164 in the groove between the front plate and the front edgeportion of the side plate. The channel typically has a depth of about0.1-0.5 mm. The width of the channel is typically greater than the depthand typically above 1 mm, such as above 5 mm or above 10 mm. The widthof the channel is typically below 100 mm. The length of the channel,i.e. the distance between the bottom of the trough and the void istypically below 100 mm.

An important part of the filter frame structure is the engagementbetween the side plates 112 and the front plate 110. As mentioned above,each one of the side plates 112 has been received in a respective groove126 of the front plate 110. The grooves and front edge portions of theside plates are shaped to fit together. The shape and dimensions of thegrooves may vary along the length of the groove. For example, the shapeof the groove where the troughs connect to the rim 118 is different fromthe shape of the groove between the troughs 120. Correspondingly, theshape of the front edge where the troughs connect to the rim 118 isdifferent from the shape of the front edge between the troughs. In orderto secure a proper engagement between the front plate 110 and the sideplates 112, each side plate, as shown in FIG. 2, is provided withretainment members 144, and the front plate 110 is provided with acomplementary retainment members 146 for each side plate 112. Theretainment members 144 of each side plate 112 comprise a snap-lockelement. The complementary retainment member 146 comprises a recess.When the side plate 112 is connected to the front plate 110, thesnap-lock element is received in the recess. Thereby the side plate 112is in fixed engagement with the front plate 110. The retainment membersand complementary retainment members ensure a reliable coupling betweenthe side plates 112 and the front plate 110 even without the use of anyadhesives such that the filter frame can be handled, e.g. lifted andmoved around, without the need of any temporary securing means orsimilar.

The filter frame is assembled as follows. The front plate 110,comprising the grooves 126 at the two opposite rim sides 112 a, 122 bthereof is provided. The first and second side plates 112 are providedand mounted at the front plate 110. For each side plate 112 the mountingincludes inserting a front edge portion 128 of the side plate 112 into arespective groove 126, and forcing the retainment members 144 intoengagement with the complementary retainment members 146 of the frontplate 110. Thereby a part of the filter frame 102 which is ready toreceive the media packs 104 has been assembled. In order to complete theassembling process to a complete filter assembly 100, the next step thusis to mount the media packs 104 and then the plate elements 116 of therear plate 114 are mounted, wherein they are forced into engagement withthe rear edge portions 136 such that snap-lock elements 148 of the sideplates 112 snaps into a locking position in the corresponding part ineach rear plate 116. As mentioned earlier, the filter assembly is nowready to be handled and could for example be transported to a differentlocation without the necessity of any temporary securing means orsimilar.

And then, in a last step of assembling the filter frame, an adhesive isused to seal and fixate the filter assembly 100. Adhesive is used toseal and fixate the filter packs to the troughs of the front and rearplates and to the channels of the side plates.

Adhesive may also be used to seal and fixate the connections between thefront plate, side plates and rear plate(s). The mere presence ofadhesive in the spaces between the different constructional details willprevent the snap-lock elements from leaving their locked position, whichadds rigidity to the structure even before the adhesive has cured.Obviously, curing will further increase rigidity and stability of thestructure by bonding the front plate, side plates and rear plate(s)together. Since the retainment members 144 will be glued into engagementwith the complementary retainment members, the snap-lock connection willbecome even stronger.

Thereafter, the filter frame assembly 100 is inserted and secured to afilter holding structure, such as a filter housing or filter bank grid(not shown). Typically, the filter frame assembly is clamped to thefilter holding structure by means of a plastic or metal clamp which isfixed to the filter holding structure by means of a bolt and a fly nutor similar. Thereby, the filter frame assembly can be tightly squeezedbetween the clamp and the filter holding structure without the use ofthrough bolts or similar that would jeopardize tightness of theconstruction. When in use, the forces acting on the filter media packs104 due to the air flow therethrough will be counteracted by the supportstructures and the internal tension in the front plate, such that thesealing properties between the front plate and the filter holdingstructure, and between the side plates 112 and the front plate 110, canbe maintained at all times.

While the invention has been described with reference to variousexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A molded plastic rectangular front plate for a V-type filter, saidfront plate having a front surface and a back surface, characterized inthat the back surface of the front plate comprises a support structureprotruding in a plane substantially perpendicular to the back surface ofthe front plate and extending along a major portion of the length of aside of the back surface of the front plate such that the thickness ofthe front plate in the direction from the front surface to the backsurface is increased towards the middle and reduced towards the ends ofthe front plate side.
 2. A molded plastic rectangular front plateaccording to claim 1, characterized in that the front plate ismanufactured by injection molding.
 3. A molded plastic rectangular frontplate according to any one of the preceding claims, wherein a lateralview of the support structure has the shape of a circular segment.
 4. Amolded plastic rectangular front plate according to any one of thepreceding claims, wherein the support structure is arranged to protrudeinto an opening of the filter holding structure when mounted to a filterholding structure.
 5. A molded plastic rectangular front plate accordingto any one of the preceding claims, wherein the support structure causesthe centre of gravity of the front plate to be displaced in a directionfrom the front surface to the back surface of the front plate ascompared to the same front plate side without the support structure. 6.A molded plastic rectangular front plate according to any one of thepreceding claims, wherein the presence of the support structure inducesan internal tension in the molded plastic material, which tensioncounteracts the stress on the front plate caused by the air pressureload during use.
 7. A molded plastic rectangular front plate accordingto any one of the preceding claims, characterized in that the backsurface comprises two support structures protruding in a planesubstantially perpendicular to the back surface and extendingsubstantially the length of opposite sides of the back surface of thefront plate such that the thickness of the front plate in the directionfrom the front surface to the back surface is increased towards themiddle and reduced towards the ends of the front plate side.
 8. A moldedplastic rectangular front plate according to any one of the precedingclaims, wherein the front plate further comprises an abutment surfacearranged to abut a filter holding structure when mounted thereto.
 9. AV-type filter frame for receiving at least one filter media pack, saidV-type filter frame being arranged to be mounted to a filter holdingstructure, the V-type filter frame comprising a molded plasticrectangular front plate according to any one of claims 1 to 8 having afront surface and a back surface, and first and second side platescoupled to the back surface of the front plate.
 10. A V-type filterframe according to claim 9, wherein the back surface comprises twosupport structures protruding in a plane substantially perpendicular tothe back surface and extending substantially the length of oppositesides of the back surface of the front plate, characterized in that saidopposite sides are the same sides of the front plate to which the sideplates coupled.
 11. A V-type filter frame according to claim 10,characterized in that the two support structures are arranged to abutthe side plates.
 12. A V-type filter assembly comprising a filter frameaccording to any one of claims 9 to 11 and at least one filter mediapack arranged in the filter frame.